Preventing farm nutrients from polluting waterways

The same nutrients that help farmers grow food can become a pollutant when they wash off fields and into waterways.

Michigan State University researchers are developing a new way to capture nitrogen and phosphorus from agricultural and urban runoff before those nutrients reach lakes and rivers. The goal is to recover these nutrients and turn a waterpollution problem into a resource that can potentially be reused.

Shiqiang “Nick” Zou, assistant professor in the College of Engineering, and his Electrified WAstewater Treatment and Elemental Recovery, or E-WATER, Lab have received a three-year, $1 million award from the U.S. Environmental Protection Agency to develop and test a technology called Carbon-Loaded Electrochemical Artificial Retention, or CLEAR.

CLEAR is designed to address a growing challenge: What happens to nitrogen and phosphorus from agricultural and urban runoff and how do we prevent it from harming water quality and contributing to harmful algal blooms that impact fish and other aquatic life? The goal is to capture these nutrients before they reach waterways and create opportunities to recover and reuse them rather than letting them go to waste.

“It’s a double-edged sword,” Zou said. “Nitrogen and phosphorus are important, but they are also a pollutant if we use too much.”

For Zou, that creates a challenge at the intersection of two necessities: food and clean water. How can we protect water quality without compromising food production?

The CLEAR project is designed to address that challenge by intercepting runoff and removing a major portion of its nitrogen and phosphorus before the water reaches waterways.

“Phosphorus is predominantly from minerals and rocks, and it’s usually considered a nonrenewable resource,” said Zou. “We only have so much phosphorus available on Earth, so we really want to reuse and recycle it when we can.”

Using electricity to capture nutrients

The new approach grew out of Zou’s 15 years of research on nitrogen and phosphorus removal. His earlier work focused on biological systems that use bacteria to remove nutrients.

Wetlands already provide a natural way to retain nutrients from water. Other approaches use materials containing metals such as iron, aluminum, calcium or magnesium to capture nutrients.

Zou’s team is taking a different approach: Instead of relying only on natural processes, the researchers are creating an engineered system that mimics the nutrient-retaining functions of a wetland using carbon and a small amount of electricity to help pull nutrients out of water.

Carbon materials capture nitrogen and phosphorus, while electricity enhances the system’s performance. The electricity used in this process could eventually come from renewable sources such as solar power.

The researchers have already developed small, bench-scale laboratory systems that use carbon materials to remove nitrogen and phosphorus from water.

“Agriculture is critically important to our state and national economies,” said Peter Savolainen, chair of the Department of Civil and Environmental Engineering. “Dr. Zou is finding innovative ways to both address the underlying concerns about pollution and also to reuse these nutrients for other purposes. We are grateful for the EPA’s support of this critical research.” 

From the lab bench to a farm

The next challenge is to determine whether the technology can perform under real-world conditions — and whether it can eventually be used on farms.

During the first stage of the project, the team plans to test water samples collected from local farmland. Later, researchers plan to deploy smaller systems at the edges of agricultural fields and divert a portion of farm drainage through them.

The project includes collaborators at the University of Wisconsin–Madison, Texas A&M University and the University of South Alabama. Testing in Michigan, Wisconsin, Texas and Alabama will allow the researchers to see how the technology performs under different agricultural and runoff conditions.

That field testing is important because it will help evaluate the system’s performance and help determine whether it could be practical for farmers to apply it to their agricultural operations.

Designing technology farmers can use

Zou’s team plans to work with farmers as the project progresses, seeking input on practical questions such as cost, installation, maintenance and how a nutrient-removal system could fit into existing farm operations. In early November, Zou will travel to Mobile, Alabama, to participate in an EPA Farmers to Farmers workshop and hear directly from farmers about their needs and concerns.

“Many times, we don’t see the concerns farmers have,” Zou said. “Those concerns could include cost, logistics and whether potential chemicals could be released that may affect their produce.”

That feedback could help researchers refine the technology while it is still being developed.

The broader goal is to create a system that can protect water quality while supporting agriculture — and potentially recover nitrogen and phosphorus that would otherwise be lost to the environment.

“We do need those infrastructures in place to help reduce pollution and help to curb the footprint,” Zou said.

Lessons from the project could also help address nutrient runoff throughout Michigan and the Great Lakes, while providing a model that could be adapted to other watersheds across the country.